Vertebrate Skulls

Vertebrate Skulls

To the tune of “Rolling in the Deep” by Adele

[Verse 1]
The first part is the chondrocranium
It encloses the brain and the sensory organs
In the different clades of vertebrates
The chondrocranium undergoes different fates
In agnathans and the chondrichthyans
The chondrocranium remains cartilage
In bony fishes, the cartilage remains
Surrounded by dermal bone — the dermatocranium

[Pre-Chorus] 
In embryonic tetrapods
This cartilage template is replaced by bone
Through endochondral ossification
And surrounded by dermal bone

[Chorus] 
Synapomorphic traits
Of the vertebrates
Include neural crest cells
And the presence of a cranium

[Verse 2] 
The splanchnocranium is the second part
It arises from the pharyngeal arches
Arch 1 is the mandibular arch
The palatoquadrate and the mandibular cartilage

 [Pre-Chorus]
The hyoid arch is the main site of
Attachment for the jaw to the chondrocranium
In the tetrapods this is not required
This bone forms the stapes

 [Chorus] x2
Synapomorphic traits
Of the vertebrates
Include neural crest cells
And the presence of a cranium

[Bridge]
The third part is the dermatocranium
This structure is not present in chondrichthyans
Of dermal bone it is composed
It forms the roof of the skull and the facial bones

[Breakdown] 
Reptile jaw joint, articular and quadrate
In mammals these bones form
The malleus and incus
The jaw joint is the squamosal and dentary

[Chorus] x2 
Synapomorphic traits
Of the vertebrates
Include neural crest cells
And the presence of a cranium